This invention relates to a scroll compressor suitable to the use thereof as a compressor for a room air conditioner and a car air conditioner.
In a conventional scroll compressor, the outer peripheral portion of an orbiting scroll member is held between a stationary scroll member and a stationary member, and a space formed on the rear surface of an end plate of the orbiting scroll member and a working chamber having an internal pressure equal to the suction pressure in the mentioned space and formed by the wraps of the two scroll members, which is disclosed in Japanese Patent Laid-open No. 148994/1980 and the corresponding U.S. Pat. No. 4,365,941.
The closed space on the rear side of the end plate of the orbiting scroll member and the working chamber being in compression stroke are communicated with each other via small ports formed in the end plate of the orbiting scroll member, thereby to maintain the pressure in the space at a level between the levels of the suction pressure and the discharge pressure. Consequently, the orbiting scroll member is pressed from the rear surface thereof, so that it closely contacts with the stationary scroll member (U.S. Pat. Nos. 4,365,941 and 4,475,874).
Another conventional scroll compressor is constructed so that the whole of the axial thrust applied to an orbiting scroll member is supported by a thrust bearing provided on the rear surface of an end plate of the orbiting scroll member. In this scroll compressor, the axial thrust is lessened by using a fluid pressure (Japanese Patent Laid-open No. 148087/1982 and the corresponding U.S. Pat. No. 4,065,279).
In these conventional techniques, it is necessary to provide seal portions on the outer side of the wraps of the two scroll members. Therefore, the outer diameters of the scroll members and the weight of the orbiting scroll member increase. This causes the centrifugal load during a high speed operation of the scroll compressor to excessively increase.